The invention relates to a method for receiving radio signals in a receiving device and a receiving device configured for carrying out the method. The receiving device tracks via an internal radio receiver, i.e. one integrated into the receiving device, which is configured to carry out, in the course of reception processing of the radio signals received in a radio channel, a channel estimation for error correction in a manner known per se.
Such a channel estimation is based on the fact that a measure for the distortion of the radio channel is formed by a Fourier pair which consists of a channel pulse response in the time domain of a channel transfer function in the frequency domain. During a channel estimation, one of the two variables channel pulse response or channel transfer functions is determined from data added to the signal to be transmitted, which are also designated as pilot information. This pilot information serves as reference to the receiver during the carrying out of the estimation of the channel characteristics. A channel estimation can then be applied to the received radio signals in order to carry out an error correction. Such a reception processing is necessary as a rule because the conditions of reception of radio receivers for radio systems are impaired, as a rule, by multipath reception. This applies to radio systems such as VHF, shortwave, mediumwave, longwave, digital radio mondiale (DRM), digital audio broad-casting (DAB), digital video broadcasting (DVB) or the like. The reason for this lies partially in a frequency-selective fading which is caused by scattering objects in the terrain. This applies both to stationary and also for mobile radio receivers. Whereas mobile radio receivers can change the situations of reception by changing the environment of reception, this remains the same in the case of stationary radio receivers so that appropriate possibilities of correction absolutely necessary.
Examples of stationary radio receivers are television sets and radio sets in apartments. In the case of mobile radio receivers, too, for example in vehicles (car radios) there are special cases in which the radio receiver is stationary for a number of minutes. Examples of this are waiting situations at rest stops, in front of the apartment of the car owner, at observation points during excursions or at parking places when shopping. This results in a virtually stationary situation of the receiver even if the receiving device as such is mobile.
The finding of whether the relevant radio receiver of a receiving device which is mobile per se is at least virtually stationary occurs in the case of motor vehicles, in general by evaluation of position information of a satellite locating system such as, e.g., from the Global Position System (GPS) which is available in most vehicles.
It is known to provide measures against effects from the multi-path reception in radio systems and to improve the signal quality. For example, the orthogonal frequency division multiplex method (OFDM) is known for this purpose, which is exclusively carried out in the radio receiver. In this context, a corresponding equalization of the signals, the radio channel estimation and the decoding of the signals takes place. This is subsequently also termed reception processing. This reception processing is carried out by corresponding calculations in a computer unit of the radio receiver.
Frequently, however, no corrections can be carried out within the radio receiver which lead to an adequate signal quality.
It is the object of the present invention, therefore, to achieve an improved reception processing of radio signals.